What about an eggnog smoothie? You could then blend in crushed ice, yogurt etc. which will diminish the sweetness but keep in the rich experience of the original! (I haven't actually tried this but I'm going to...)

What about making a Tom and Jerry? See http://www.americanfoodroots.com/50-states/holiday-drinks-bring-back-the-tom-and-jerry/
Or perhaps experiment, replacing some of the cream with almond milk or coconut milk.